If you have a macro you would like available to all workbooks you open in Excel, save it in a workbook located in C:\Documents and Settings\username\Application Data\Microsoft\Excel\XLSTART\personal.xls.

This is useful if, say, your department minion sends out spreadsheets showing everybody's training requirements, and you'd prefer to extract just the new ones that apply to you. And you know that convincing her to include your macro in her spreadsheet is unlikely to succeed.